Carpometacarpal (cmc) joint arthroplasty implants and related jigs and methods

ABSTRACT

Thumb carpometacarpal (CMC) joint implants include a trapezium implant defining an articulating surface and a cooperating first metacarpal implant with a base portion of the first metacarpal defining an articulating surface. The first metacarpal base articulating-surface is configured to articulate against the trapezium implant articulating surface.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/005,882, filed Jan. 13, 2011, which is a continuation of U.S. patentapplication Ser. No. 12/109,511, filed Apr. 25, 2008, which claims thebenefit of priority of U.S. Provisional Application Ser. No. 60/914,449filed Apr. 27, 2007, the contents of which are hereby incorporated byreference as if recited in full herein.

FIELD OF THE INVENTION

This invention relates to implants suitable for use in treating painand/or injury of the carpometacarpal joint.

BACKGROUND OF THE INVENTION

Basilar thumb arthritis (arthritis at the base of the thumb) of thecarpo-metacarpal (CMC) joint is thought to be the most common arthritisof the homosapien. It typically presents as a symptomatic problem in thesixth decade of life and its incidence increases thereafter. It is aresult of the rather recent phylogenetic appearance of a highly mobile,strong thumb ray. The thumb acts as the pivotal and guiding member ofthe defining anatomical features of the human, the prehensile hand. Thebrain's cortical representation area of the thumb is huge. The thumballows for a panoply of activities from watch making to weightlifting.Unfortunately, this distinct anatomical advantage can result inarthritis of the CMC joint of the thumb.

It is believed that gaming and cell phone text-messaging and the likemay also lead to basilar thumb arthritis, with a resulting increase inincidence as well as a potential earlier onset that has beenconventional.

Anatomically, the CMC joint includes the trapezium articulating with thebase of the first metacarpal as shown in FIG. 1. As shown in FIG. 2, theCMC joint is a saddle joint allowing abduction toward the palm,abduction away from the palm, opposition (toward the 5^(th) finger), andextension or retroposition (backward or hitch-hiker position.) As shownin FIG. 3B, the articular surface of the base of the 1^(st) metacarpal20 is divided into dorsal and palmer slopes and a central saddleportion. As shown in FIG. 3A, the opposing articular surface of thetrapezium 10 also has two parts: a spherical portion 11, whicharticulates with the slopes of the first metacarpal; and a saddleportion 12, which articulates with the saddle portion of the 1^(st)metacarpal. (See, e.g., Zancolli et al., Biomechanics of thetrapezio-metacarpal joint, Clinical Orthopaedics and Related Research,No. 220, July 1987, pp. 14-26). FIG. 3C illustrates an enlarged “normal”or “natural” trapezium 10 and first metacarpal base 20 b.

The subchondral (below cartilage) bone of the trapezium-first metacarpalis covered by hyaline cartilage. This cartilage is typically the firsttissue to deteriorate during arthritic wear of the joint. Initially,thinning and pitting occurs, which can be followed by osteophyte (bonespur) formation and subluxation (loss of congruity) of the joint.

Over the past fifty years various arthroplasties have been proposed totry to alleviate the disabling pain of CMC arthritis. Generally stated,the arthroplasties have been either soft tissue interpositions, implantinterpositions, or partial joint replacements using implants. Theimplant procedures either have replaced the base of the first metacarpalor replaced the trapezium following trapezectomy.

Currently, 1^(st) metacarpal implants involve inserting anintramedullary stem into the base of the. 1^(st) metacarpal, to which isattached a convex articular surface replacement. Trapezial implantsgenerally have the shape of the anatomic trapezium. In both cases, animplant material (e.g., metal, silicone, or ceramic) articulates with abone surface where motion occurs. These procedures do not attempt toreplace the joint but rather act as spacers. Fortunately, they canreduce the arthritic pain, but problems have arisen. Potential problemsinclude implant loosening, implant breakage, implant dislocation,adverse tissue reaction to the implant (particularly silicone), failureof pain relief, loss of strength, and implant subsidence (sinking in orerosion of the residual trapezium, as in 1^(st) metacarpal implants). Itis believed that because of these problems, the most common procedurecurrently performed for CMC arthritis is a soft tissue interpositionsuspension procedure also known as “ligament reconstruction with tendoninterposition (LRTI)” where no implant is used.

In view of the foregoing, there remains a need for alternative thumb CMCimplants.

SUMMARY OF EMBODIMENTS OF THE INVENTION

In some embodiments, thumb CMC joint implants include a trapeziumimplant defining an articulating surface and a cooperating firstmetacarpal implant with a base portion of the first metacarpal definingan articulating surface. The first metacarpal base articulating-surfaceis configured to articulate against the trapezium implant articulatingsurface.

Embodiments of the present invention can replace both the base of thefirst metacarpal and the opposing articular surface of the trapezium,resulting in a total thumb CMC arthroplasty (TCMA).

In some embodiments, the trapezium implant includes at least onedownwardly extending anchoring member. The at least one anchoring membercan include a plurality of transversely spaced apart keels extending atleast a major portion of a length or width dimension of the trapeziumimplant.

In some embodiments, the trapezium implant can include a projectingportion that forms the articular surface. The first metacarpal baseportion can include a recessed cavity that matably receives theprojecting portion of the trapezium implant, thereby allowingarticulating motion between the trapezium implant and the firstmetacarpal base.

The trapezium implant can have a projecting portion that extends outsidethe bounds of the trapezium into the CMC cavity to define asubstantially convex articular surface. The first metacarpal implantbase portion can have a socket with a substantially concave cavity sizedand configured to matably receive the projecting portion of thetrapezium implant.

Other embodiments are directed to medical kits for thumb CMC jointarthoplasty. The kits include: (a) at least one trapezium implant; (b)at least one first metacarpal intramedullary stem implant; and (c) aplurality of base members having different sizes and/or shapes, each ofthe base members configured to serially attach to the first metacarpalintramedullary stem implant. In position, the attached base member ofthe intramedullary implant and the trapezium implant articulate againsteach other.

In some embodiments, the at least one trapezium implant includes atleast one downwardly extending anchoring member configured to reside inlocal bone of a target trapezium.

The medical kits can also include a plurality of trial trapeziumimplants. The trials have a substantially planar bottom surface and canhave a non-binding fin or keel or are devoid of a downwardly extendinganchoring member.

The medical kits may also include at least one trapezium implant jigconfigured to define a bone preparation guide or template for preparinga target trapezium to accept the trapezium implant.

Still other embodiments are directed to jigs for a thumb CMC arthoplastyprocedure. The jigs include a rigid body having a substantially planartop segment that merges into a substantially planar downwardly extendingside segment and at least one slot extending across at least a portionof the top segment and down into at least a portion of the side segment.The slot is sized and configured to define a cutting guide for a targettrapezium.

In particular embodiments, the slot is substantially straight andsubstantially horizontal across the top segment and substantiallyvertical along the side segment.

Other embodiments are directed to methods for treating and/or repairinga CMC joint in a patient. The methods include: (a) implanting atrapezium implant in a target trapezium so that the trapezium implantdefines an articulating surface; and (b) implanting a first metacarpalimplant into the first metacarpal so that the first metacarpal implantdefines an articulating surface that articulates against the trapeziumimplant articulating surface.

In some embodiments, the methods also include, before the step ofimplanting the trapezium implant: (i) preparing the target trapezium forreceiving the trapezium implant by planarizing the natural articularsurface of the target trapezium, then fanning a channel in the targettrapezium; and (ii) trying different size trapezium trials to determinea proper size trapezium implant for the patient.

The methods may also include, before the step of implanting thetrapezium implant, temporarily affixing a jig with a drilling andcutting channel guide to the trapezium, and drilling and cutting achannel into the target using the jig drilling and cutting channelguide.

In some embodiments, the first metacarpal implant comprises an elongateintramedullary stem and an attachable base member with a socket, and themethod further includes, before the step of implanting the firstmetacarpal implant, trying different size base members to select a basemember that substantially fills the CMC cavity.

The foregoing and other objects and aspects of the present invention areexplained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anatomical drawing of the palmar aspect of the carpal andmetacarpal bones illustrating the 1st metacarpal, the CMC joint and thetrapezium.

FIG. 2 is an axial view illustrating motions of the thumb.

FIGS. 3A and 3B are schematic illustrations of the bones of thetrapezio-metacarpal joint (the upper bones associated with the trapeziumand the lower bones associated with the metacarpal).

FIG. 3C is an enlarged schematic illustration of the correspondingarticular surfaces of the metacarpophalangeal joint (the trapezium andthe first metacarpal base).

FIG. 4A is a side perspective view of a 1st metacarpal implant with acooperating trapezium implant according to embodiments of the presentinvention.

FIG. 4B is an end view of the 1st metacarpal implant shown in FIG. 4A.

FIG. 4C is an exemplary end view of the trapezium implant shown in FIG.4A according to some embodiment of the present invention.

FIG. 4D is a top perspective view of an alternate configuration of thedistal end member (the shape being similar to the natural articularsurface of the CMC joint) according to some embodiments of theinvention.

FIG. 5A is an enlarged side view of the trapezium implant shown in FIG.4A.

FIG. 5B is an enlarged side view of an alternate configuration of thetrapezium implant shown in FIG. 4A.

FIG. 5C is an enlarged end view of the trapezium implant shown in FIG.5A or 5B.

FIG. 5D is an enlarged end view of an alternative configuration of thetrapezium implant shown in FIG. 5A or 5B according to some embodimentsof the invention.

FIG. 6 is a schematic illustration of a thumb with a region of thetrapezium removed to define a prepared distal surface suitable for thetrapezium implant according to embodiments of the present invention.

FIG. 7A is a side View of an intramedullary implant portion of a 1stmetacarpal implant configured to matably attach to a selected distal endmember (facing the trapezium).

FIG. 7B is an opposing side view of the distal end member shown in FIG.7A.

FIG. 7C is a side view of an articulating base member for a saddleconfiguration of the 1st metacarpal with the intramedullary portion ofthe implant in position and the distal end member attached thereto andextending beyond the bounds of the metacarpal to define an articularsurface according to some embodiments of the present invention.

FIG. 7D is a side view of an alternate attachment configuration for theintramedullary member and the distal end member according to otherembodiments of the invention.

FIG. 8 is an exploded view of an alternate configuration of thetrapezium implant and the cooperating 1st metacarpal implant accordingto yet other embodiments of the invention.

FIGS. 9A and 9B are schematic illustrations of a trapezial jig accordingto embodiments of the invention.

FIG. 10 is a schematic illustration of a drill that extends through thejig shown in FIGS. 9A and 9B to define an anchoring tunnel, aperture orhole for the trapezial implant according to some embodiments of theinvention.

FIG. 11A is a schematic illustration of a saw that extends through thejig shown in FIGS. 9A and 9B to connect the anchoring holes with adistal cut surface of the trapezium according to embodiments of theinvention.

FIG. 11B is a schematic illustration of a surgically prepared trapeziumaccording to embodiments of the invention.

FIG. 12 is a schematic illustration of a broach that can be used to sizethe 1st metacarpal implant. A trial can be inserted to determine theappropriate implant size.

FIG. 13A is a schematic illustration of a medical set or kit ofdifferent sized trapezium trials according to embodiments of the presentinvention.

FIGS. 13B and 13C are alternate end views of other trapezium trialsaccording to embodiments of the present invention.

FIG. 14 is a schematic illustration of a medical set or kit of differentcomponents for a CMC total joint replacement procedure according toembodiments of the invention.

FIG. 15 is a flow chart of exemplary operations that can be used tocarry out embodiments of the invention.

FIGS. 16-23 illustrate exemplary steps that can be used to surgicallyimplant a total TCMA prosthesis according to embodiments of the presentinvention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying figures, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. Like numbers refer to like elementsthroughout. In the figures, certain layers, components or features maybe exaggerated for clarity, and broken lines illustrate optionalfeatures or operations unless specified otherwise. In addition, thesequence of operations (or steps) is not limited to the order presentedin the figures and/or claims unless specifically indicated otherwise. Inthe drawings, the thickness of lines, layers, features, componentsand/or regions may be exaggerated for clarity and broken linesillustrate optional features or operations, unless specified otherwise.

It will be understood that when a feature, such as a layer, region orsubstrate, is referred to as being “on” another feature or element, itcan be directly on the other feature or element or intervening featuresand/or elements may also be present. In contrast, when an element isreferred to as being “directly on” another feature or element, there areno intervening elements present. It will also be understood that, when afeature or element is referred to as being “connected”, “attached” or“coupled” to another feature or element, it can be directly connected,attached or coupled to the other element or intervening elements may bepresent. In contrast, when a feature or element is referred to as being“directly connected”, “directly attached” or “directly coupled” toanother element, there are no intervening elements present. Althoughdescribed or shown with respect to one embodiment, the features sodescribed or shown can apply to other embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andshould not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein. The term “polymer” includes copolymers andderivatives and/or combinations thereof.

The implant can be a total joint replacement implant that allowsarticulation of the bones. The term “total joint replacement” means thatboth the base of the first metacarpal and the opposing articular surfaceof the trapezium are replaced with cooperating implant surfaces,resulting in a total thumb carpo-metacarpal arthroplasty (TCMA), therebyproviding complete joint replacement as in total hip arthroplasty (THA)or total knee arthroplasty (TKA).

As shown in FIG. 4A, embodiments of the invention provide anintramedullary first metacarpal implant 40 that cooperates with atrapezium implant 60. The first metacarpal implant 40 includes a baseportion 45 that defines a base of the CMC joint. As shown, the baseportion 45 has a socket 46 (FIG. 4B) that matably receives theprojecting portion 61 of the trapezium implant 60, allowing articulationbetween the two implants 40, 60 such that the corresponding articulatingsurfaces 40 s, 60 s articulate against each other. In the embodimentshown in FIG. 4A, the first metacarpal implant 40 has a substantiallyconcave articulating surface 40 s substantially matched to a convexarticulating surface 60 s of the trapezium implant 60. The firstmetacarpal implant 40 can be a single unitary member or can include amatable base member that defines the articulating surface 40 s. Forexample, if the implants 40, 60 comprise pyrocarbon or a similarlylubricious and/or strong composite or polymer, the two surfaces 40 s, 60s can articulate against each other without requiring an intermediarymaterial or component. Alternatively, if the first metacarpal implant 40and trapezium implant 60 are made out of stainless steel or titanium orother suitable biomedical metal, then a base member (typically attachedto the first implant 40) can be used to define one of the articulatingsurfaces, formed of a suitable biocompatible material, such as, forexample, polyethylene (so that there is no “metal on metal” contact forthe articulating surfaces 40 s, 60 s).

In other embodiments, the first metacarpal implant 40 can include a baseportion 45 that is shaped as a substantially anatomically equivalent ofa natural metacarpal base (FIGS. 3B and 3C) and, similarly, thetrapezium implant 60 can have a corresponding substantially naturalanatomic distal articular surface that can cooperate with the firstmetacarpal implant 40. Examples of implants 45, 60 with alternativearticulating surfaces 40 s, 60 s having more natural surface contoursare shown in FIG. 4D. The implants 40, 60 can thus define a naturalanatomical contour of the CMC joint to act as a resurfacing implantsystem.

FIG. 4B is an end view of the base portion 45 of the first metacarpalimplant 40 shown in FIG. 4A that can define a receiving socket 46 withthe articulating surface 40 s forming part of the CMC replacement joint.The socket 46 can have a width “W₁” with an overall width of the baseportion 45 can have a width “W₂”. The implant 40 can be provided indifferent sizes with different widths, recognizing that the anatomicalconstraints and needs will likely vary by patient (age, gender, bonestructure and the like). In some embodiments, the socket 46 has aconcave hemispherical shape with an arc radius R₁.

FIG. 4C illustrates an end view of the trapezium implant 60 shown inFIG. 4A. As shown, the implant 60 includes at least one anchoring member63, shown as two keels 63 ₁, 63 ₂. More or fewer anchoring members 63can be used and different anchoring member configurations may also beused. FIG. 4A illustrates that the anchoring member 63 can be orientedto extend transversely across at least a major portion of the width ofthe implant 60.

The keels 63 ₁, 63 ₂ are typically rigid and reside in a bone tunnel orchannel formed in the trapezium, but may be flexible and/or otherwiseconfigured to promote and/or allow for local tissue ingrowth. Theimplant 60 can have a substantially planar bottom mounting surface 62and the at least one anchoring member 63 can extend below the bottomsurface 62. As shown, the anchoring member 63 can extend downwardlysubstantially orthogonal to the mounting surface 62, but the anchoringmember 63 may be oriented at different angles.

The thickness T₁ of the projecting portion of the trapezium implant 60can vary to allow a clinician to select the size that substantiallyfills the target CMC cavity. Sets of the implant 60 can be provided withdifferent thickness T₁ to allow a clinician to select an appropriate onefor the patient, as, again, the desired thickness may vary due to targetanatomical considerations, age, gender and the like. The downwardlyextending length of the anchoring member 63 (e, g., keels 63 ₁, 63 ₂),is typically between about 0.1 inch to about 0.25 inches, defining anoverall thickness T₂. In some embodiments, the projecting portion (e.g.,dome) 61 can have a convexity with a radius R₂ that may, in someparticular embodiments, be between about ⅛ inch to about ⅜ inches, whichis typically slightly less than that of the socket radius R₁, therebyallowing for an articulating snug fit to inhibit misalignment orseparation during articulation.

FIG. 5A is an enlarged side view of the trapezium implant 60. As shown,the at least one anchoring member 63 can reside inside the bounds of thebottom surface 62 and terminate prior to the outer portions thereof.FIG. 5B illustrates that the at least one anchoring member 63 can extendcloser to one outer side edge of the implant than the opposing sideedge. FIG. 5C illustrates that the at least one anchoring member 63 canhave a larger and/or differently configured lower portion 64. As shown,the at least one anchoring member 63 can have a substantially thinplanar body that merges into a substantially circular (cross-section)lower portion 64. As will be discussed further below, the lower portioncan reside in a correspondingly shaped tunnel or channel in local boneto help retain the implant in a desired position. Alternatively, or incombination with the anchoring member(s) 63, bone cement or otheranchoring mechanisms may be used. FIG. 5D illustrates an alternativeanchoring member configuration, located substantially medially on theimplant body 60. The lower portion 63 may be flexible and able to bepress fit into a holding bone channel or tunnel. Combinations of theabove anchoring configurations or other configurations may also be used.

To prepare the surgical site for the implants 40, 60, the base of the1^(st) metacarpal can be planarized and/or flattened and theintramedullary implant 42 can be inserted into the proximal portion ofthe 1^(st) metacarpal 20. Similarly, as shown in FIG. 6, the distalarticulating portion 10 r of the anatomic trapezium can be removed toflatten and planarize the implant support surface and the implant 60 canbe attached to the remaining trapezium. The first metacarpalintramedullary component 42 can be selected to fill and match thecontour of the target endosteal (inside) surface of the proximal aspectof the first metacarpal 20. FIG. 7A illustrates that the implant 40 caninclude a base portion 45 that is matably attachable to theintramedullary portion 42 (e.g., stem). The intramedullary portion 42 ofthe implant 40 can be provided in various sizes to allow for correctpatient sizing. Similarly, the base portion 45 can be provided indifferent sizes and/or configurations to allow a clinician to select theappropriate size for a patient.

In some embodiments, the implants 40, 60 can be provided in S, M, L andXL sizes, such as in the exemplary sizes provided below. The size of thetrapezium implant 60 will determine the desired size of the firstmetacarpal implant 40, making the size of the trapezium implant 60determinate thereof.

Size Trapezium Radius 1st MC base member Small 3-4 mm (typically aboutmatching ⅛ inch (3.18 mm)) Medium 5-7 mm (typically about matching ¼inch (6.35 mm)) Large 8-10 mm (typically about matching ⅜ inch (9.52mm))

The intramedullary surface 42 s of the implant 42 can be roughened(cintered, pitted, scraped, filed, contoured, etc.) to promote boneingrowth. The intramedullary implant 42 can be press fit into position,but also or alternatively can be cemented in with suitable biocompatiblecement, such as, for example, polymethylmerthacolate. The intramedullaryimplant 42 can be manufactured out of various substantially rigidbiocompatible materials, such as metals, rigidized polymers, ceramics,and/or carbon. As shown in FIG. 7A, the intramedullary implant 42 caninclude a locking member 44 to mate to the base portion 45 which definesthe articular component. FIG. 7A shows that the locking member 44 can bea trunnion or post and FIG. 7B illustrates that the base portion 45 caninclude an aperture or channel 49 sized and configured to matablyreceive the locking member 44. FIG. 7C illustrates that the base portion45 with the 1^(st) MC articulating component can have a saddle(“natural”) configuration and may be snap-fitted and/or locked onto theproximal portion of the 1^(st) MC intramedullary component 42. FIG. 7Dillustrates that the base portion 45 can include the locking member 44while the intramedullary implant 42 can include the correspondinglocking aperture 49. In other embodiments, the first metacarpal implant40 can be pre-formed at an OEM or offsite location or defined by asingle member (not shown).

In some embodiments, the intramedullary implant 42 and the trapeziumimplant 60 are metallic while the base portion 45 can comprise a polymerthat provides the articulating surface 40 s with the desired slidingfrictional and/or lubricity property. The base portion 45 can be formedof a unitary member and material, similar to a spacer. In someembodiments, the base portion 45 comprises polyethylene. It can beprovided in varying thicknesses as discussed herein in order tosubstantially fill the articulating cavity of the CMC joint. As alsonoted above, the articulating surface 40 s can be substantially concavein shape but also can be fashioned more like an anatomic 1^(st) MCarticular surface (e.g., saddle shaped), as noted above (see, e.g.,FIGS. 4D, 7C).

The trapezial implant 60 has an articulating surface 60 s that can begenerally and/or substantially convex but also can be saddle shaped. Theconvex shape can reduce the stresses on the component at the boneimplant interface.

FIG. 8 also shows that the trapezium implant 60 can define a socket thathas a substantially concave articulating surface 60 s while the baseportion 45 of the first metacarpal implant 40 can be substantiallyconvex. The concave shape may reduce the stresses on the component atthe bone implant interface.

The anchoring member 63 of the trapezium implant 60 can be configured tobe resistance-fitted. The keel(s) and/or anchoring portion of theimplant 60 can be forced into position by hammering, pushing and/orforcibly sliding the implant 60 into place. The placement can be done byovercoming the friction of the trapezial bone against the implant 60. Ajig or series of jigs can be employed to prepare the implant bone siteto facilitate the implantation (see, for example, an exemplary surgicalprocedure described below). The lower bone contact surface of theimplant 60 and/or anchoring member(s) 63 can be roughened to promotebone ingrowth. The trapezium implant 60 can be configured to withstandloosening forces. The implant system can allow early motion, obviatingthe need for a cast post-operatively.

Surgical Procedure

It is contemplated that the implantation procedure should be able to becompleted in less than about 1.5 hours. It may be performed underintravenous block anesthesia, but axillary block or general anesthesiaare additional options. During the surgical procedure, the hand istypically in the palm up or semi-supinated position. A Wagner approachcan be used, taking down the thenar muscles to expose the CMC capsule. Asuitable needle, such as an 18-gauge needle, can be inserted into theCMC joint, identifying the joint. The CMC capsule can be incisedaxially, in line with the joint surface, taking care to preserve thecapsular attachments to the trapezium and the base of the firstmetacarpal. The capsular cut can be made closer to the trapezium sincethe capsular attachment to the base of the 1^(st) MC is tenuous. Asshown in FIG. 6, a wafer of bone comprising the articular surface is cutfrom the distal aspect of the trapezium with a suitable cutting member,such as, for example, a microsagital saw. This cut can be flat and madeparallel to the scapho-trapezial joint, that is, perpendicular to thelong axis of the trapezium. A thin wafer of articular surface can alsobe cut from the proximal aspect of the base of the first metacarpal(1^(st) MC).

Next, as shown in FIG. 9A, a trapezial jig 80 is applied to thetrapezium 10 with its flat top surface 81 placed against the distal cutsurface of the trapezium. The jig 80 can be rigid and may be metallic.The jig 80 has a top segment 80 s that merges into adownwardly-extending side segment 80 s. The jig 80 can include cuttingand drilling guide channels 83 and holding apertures 81 a that allowpins, staples, nails, screws, wires and/or sutures to hold the jig 80 inposition. The drilling and cutting guide channels 83 can be slots thatextend across the top segment 80 s down through at least a major portionof the side segment 80 s. Although shown with two channels 83, the jig80 can include one channel or more than two channels, typicallycorresponding to the number of anchoring members 63 (FIG. 5C). Also asshown, the channels 83 can end at a keyhole 84 that is sized andconfigured to correspond to a shape that can receive the lower portionof the anchoring member 63. As shown, the shape is circular, and may besized to be the same or slightly less than the size of the lower portionof the anchoring member 64 for frictional fit thereof.

As shown in FIG. 9B, in some embodiments, a plurality of holding members82, such as 0.35 or 45 kirschner wires, can be used to secure the jig 80to the trapezium 10. FIG. 10 illustrates a suitably sized drill bit 85(e.g., a 3/32″ drill bit) with a stop feature can be used to drill thelower anchoring holes 164 (FIG. 11B) for the trapezial implant 60.Referring to FIGS. 11A and 11B, a cutting member 86, such as amicrosagital saw, can be used to form bone tunnels or channels 163 thatconnect the anchoring holes 164 with the distal cut surface 10 s of thetrapezium to form a prepared implant site 10 p as shown in FIG. 11B. Thecutting may be done with a knife rather than a saw. Also, the cuttingmay be done before or after the drilling.

The trapezial jig 80 can be removed and the thumb ray can be extendedand adducted to expose the base of the 1^(st) MC for intramedullarysizing. As shown in FIG. 12, broaches 90 can be inserted to size the1^(st) MC. Intramedullary trials 190 (FIG. 22) can be used to select anintramedullary implant 40 or 42 of the desired size. Trapezial trials100 can also be inserted to establish a suitable trapezium implant 60size/configuration. As shown in FIG. 13A, the trapezium trials 100 a,100 b, 100 c (corresponding to different sizes) can be provided as a kit100. In FIG. 13A, the trials 100 a-c do not include the anchoringmember(s) 63. However, as shown in FIGS. 13B and 13C, the trials 100 a(only one trial is shown) can include at least one relatively thin fin101 that can fit into the anchoring member channel and act as a postthat can inhibit rotation during the trialing (but do not bind or lockinto position). The thumb ray is distracted and the space created issized. A 1^(st) MC trial 190 (typically without the 1^(st) MCarticulating surface) can be attached to the 1^(st) MC intramedullarytrial. Range of motion is tested. The final implants 42, 45, 60 can beinserted in the following order: 1^(st) MC intramedullary implant 42,trapezial articulating implant 60, and 1^(st) MC articulating implant45. Once positioned, the surgeon can proceed with capsular, muscle andskin closure and can optionally reinforce the capsule with a GRAFTJACKET reinforcement (Wright Medical Technologies). A removable thumbspica splint can be used for support and range of motion can beginearly.

FIG. 14 illustrates an exemplary medical kit 125 that can include trialbase implants 145, trial trapezium implants 100 a, 100 b, a selection ofdifferent size actual implants 42, 45, 60 (or these may be providedseparately in individual sterilized sealed packages) and optionallybroaches 90 and/or intramedullary trials 190 (not shown), all in asterile package or packages. The kit 125 may also include the jig(s) 80,saw 86 and/or drill bit 85 (with or without drill).

FIG. 15 is a flow chart of exemplary operations that can be used tocarry out embodiments of the invention. As shown, a trapezium implantcan be implanted in a target (prepared) trapezium so that the trapeziumdefines an articulating surface of a CMC joint in a patient (block 200).

In some particular embodiments, the target trapezium can be prepared forreceiving the trapezium implant by planarizing the natural articularsurface of the target trapezium (removing a thin wafer), then forming atleast one channel in the target trapezium (block 202). Different sizetrapezium trials can be positioned in the CMC joint to determine aproper size trapezium implant for the patient (block 204).

In some embodiments, before the step of implanting the trapeziumimplant, a jig with a drilling and cutting channel guide can betemporarily affixed to the trapezium, and at least one channel can bedrilled and/or cut into the target trapezium using the jig drilling andcutting channel guide (block 206).

The first metacarpal implant can include an elongate intramedullary stemand an attachable base member with a socket, and before the step ofimplanting the first metacarpal implant, the method may include tryingdifferent size base members to select a base member that substantiallyfills the CMC cavity (block 208).

FIGS. 16-23 schematically illustrate the steps in an exemplary surgicalprocedure. FIG. 16 illustrates that a Wagner incision is made. FIG. 17illustrates that a capsular incision (do not section abductor to thumb).FIG. 18 illustrates the 1st metacarpal articular resection 300 (variableaccording to space needed) and a minimal trapezium resection 400 topreserve bone for the trapezium implant 60. FIG. 19 illustrates the jig80 in position (pinned in place) and a drill 85 used to create theanchoring hole 164 for the keel 63. As shown, the drill bit 85 caninclude a stop collar to inhibit forward movement of the drill into thetrapezium at a certain distance. FIG. 20 illustrates the saw 86 forcreating the keel shaft 163 in the bone. FIG. 21 shows the thumbadducted and extended for the first metacarpal base exposure and abroach 93 used to (rasp, broach and/or prepare) an intramedullary spacefor the first metacarpal implant 40. FIG. 22 illustrates the placementof the trapezium trial 100 a (with anti-rotational fin 101) and firstmetacarpal trial 190. A clinician can measure or size the distance orsize “D” of the gap 350 created between the first metacarpal base andthe trapezial implant 60, then select the appropriate articulatingthickness. As shown, where a separate base member 45 is used, thismember 45 can define the articulating thickness. In other embodiments,the entire implant 40 can be selected from a kit to provide the desiredthickness.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few exemplary embodiments ofthis invention have been described, those skilled in the art willreadily appreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe claims. In the claims, means-plus-function clauses, if used, areintended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures. Therefore, it is to be understood that the foregoing isillustrative of the present invention and is not to be construed aslimited to the specific embodiments disclosed, and that modifications tothe disclosed embodiments, as well as other embodiments, are intended tobe included within the scope of the appended claims. The invention isdefined by the following claims, with equivalents of the claims to beincluded therein.

1. A thumb Carpo-MetaCarpal (CMC) joint implant, comprising: a thumbtrapezium implant defining an articulating surface, wherein thetrapezium implant comprises at least one keel that has a flat segmentthat merges into a second segment with a substantially circularcross-sectional shape, wherein the substantially circular shape has across-sectional size that is greater than a cross-sectional size of theflat segment, and wherein the at least one keel is configured to residein a correspondingly shaped channel formed in a target trapezium; and acooperating thumb first metacarpal implant with a base of the firstmetacarpal defining an articulating surface, wherein the firstmetacarpal base is configured to articulate against the trapeziumimplant articulating surface, wherein the trapezium implant and thefirst metacarpal implant articulating surfaces have shapes similar tonatural articular surfaces of a CMC joint; and wherein the at least onekeel is sized and configured to slidably snugly enter a thin bonechannel in a target trapezium from a volar radial surgical approach. 2.The implant of claim 1, wherein the flat segment of each respective atleast one keel has parallel, straight, outer short sides and a widththat is greater than a length of the short sides, and wherein at leastone of the articulating surfaces has a saddle shaped configuration. 3.The implant of claim 1, wherein the trapezium implant keel is sized andconfigured to snugly reside in a thin trapezium bone channel that hasparallel vertically extending sidewalls that merge into a lowermostsemi-circular portion, and wherein the flat segment of each respectiveat least one keel trapezium keel extends in a vertical orientation witha width that is greater than a length thereof, with the length beingbetween about 0.1-0.25 inches.
 4. The implant of claim 1, in combinationwith a plurality of trapezium implant trials, wherein the trials have asubstantially planar bottom surface devoid of any downwardly projectinganchoring member.
 5. The implant of claim 1, in combination with aplurality of trapezium implant trials, wherein the trials have asubstantially planar bottom surface with at least one downwardlyextending anti-rotational post, and wherein the at least one post has adifferent configuration than the implant at least one keel.
 6. Theimplant of claim 5, wherein the downwardly extending post has a planarbody.
 7. The implant of claim 1, further comprising at least onetrapezium implant trial, wherein the trials have a planar fin with alength that is shorter than a length of the keel of the trapeziumimplant.
 8. The implant of claim 1, in combination with at least onetrapezium implant jig with at least one downwardly extending flat slotwith parallel straight sides configured to define a bone preparationguide or template for preparing at least one slot in a target trapeziumfrom a volar radial surgical approach.
 9. The implant of claim 8,wherein the trapezium implant jig comprises a plurality of apertures foraccepting members to secure the jig in position during formation of theslot in the target trapezium.
 10. The implant of claim 9, wherein atleast one downwardly extending slot of the trapezium implant jig isdefined by an aperture that extends between a pair of straight verticalsidewalls of the jig that merges into a keyhole on a medial to lowerportion thereof.
 11. The implant of claim 8, wherein the jig comprises atop portion that merges into a downwardly extending side portion, withthe side portion being substantially orthogonal to the top portion, andwherein the jig at least one downwardly extending slot is configured tocontinuously extend from the downwardly extending portion upward andacross the top portion to define a substantially horizontal slotextending through a top surface of the jig.
 12. A thumb arthroplastyimplant, comprising: a first implant member having an upper surface; anda cooperating second implant member with a base portion defining a lowersurface thereof, wherein the first implant upper surface faces thesecond implant lower surface and the first implant upper surface and thesecond implant lower surface define implant articulating surfaces withcontours similar to natural articular surfaces of a CMC joint so that atleast one of the articulating surfaces has a saddle shapedconfiguration, wherein the first implant member is configured toarticulate with respect to the second implant member, wherein the firstimplant member comprises a pair of spaced apart substantially rigiddownwardly extending anchoring members, each anchoring member having aplanar portion with a perimeter with parallel straight sides thatextends downward in a depth dimension and merges into a substantiallycircular lower portion, the anchoring members extending transversely atleast a major portion of a length and/or width dimension of the firstimplant member, wherein the substantially circular portion has a greatercross-sectional size than the planar portion, and wherein the anchoringmembers are configured to slidably enter a respective spaced apartchannel formed in a target trapezium from a volar radial direction. 13.The implant of claim 12, further comprising: (i) at least one trapeziumimplant trial; and (ii) a jig defining at least one narrow channel intrapezium bone from a volar radial approach.
 14. A method for treatingand/or repairing a thumb CMC joint in a patient, comprising: forming atleast one narrow slot in a target trapezium bone from a volar radialapproach; and slidably inserting a trapezium implant comprising at leastone downwardly extending keel with a planar body that merges into anenlarged lower portion in the target trapezium bone so that the keelresides in a respective formed slot and the trapezium implant uppersurface defines an articulating surface of a CMC joint in a patient; andimplanting a first metacarpal implant into the first metacarpal so thatthe first metacarpal implant defines an articulating surface of the CMCjoint in the patient which articulates against the trapezium implantarticulating surface with the articulating surfaces having shapessimilar to that of corresponding natural articulating surfaces.
 15. Themethod of claim 14, further comprising planarizing a natural articularsurface of the target trapezium.
 16. The method of claim 14, tryingdifferent size trapezium trials to determine a proper size trapeziumimplant for the patient.
 17. The method of claim 14, wherein the formingstep is carried out by temporarily affixing a jig with at least onedownwardly extending drilling and cutting channel guide to the targettrapezium, then drilling and cutting at least one channel into thetarget trapezium from the volar-radial approach using the jig drillingand cutting channel guide.
 18. The method of claim according to claim14, wherein the at least one keel has a substantially planar downwardlyextending body that merges into a lower portion that has a largercross-sectional configuration that the substantially planar body. 19.The method of claim 17, wherein the at least one keel has asubstantially planar downwardly extending body that merges into a lowerportion that has a larger cross-sectional configuration that thesubstantially planar body, and wherein the drilling and cutting guidechannel has a corresponding configuration.
 20. The method of claim 14,wherein the slidably inserting step is carried out so that the at leastone keel snugly enters a respective slot for frictional engagement oflocal bone.